The present invention relates to heating systems and is particularly directed to improvements in domestic-type, gas- or oil-fired, hot-air heating systems.
Hot-air heating systems, broadly described, comprise a furnace having a combustion chamber for the burning of hydrocarbon fuels to produce heat which is transferred, in part, by means of a heat exchanger to air in a heating chamber. The heated air leaving the heating chamber of the furnace, usually driven by a fan or the like, is passed through suitable duct means to individual rooms of a house or like dwelling to be heated and cool air from the said rooms is reintroduced to the furnace for recycle of the dwelling air as a heating medium.
The seasonal efficiency of known domestic-type furnaces is generally very low, being in the range of about 50-65%, i.e. over the course of a year only 50 to 65% of the heating value of the fuel consumed by the furnace is utilized in heating the dwelling.
Recently attempts have been made to improve the seasonal efficiency of hot air gas furnaces with flue dampers, heat reclaimers, electronic ignition and other energy saving devices. These modifications have only improved the seasonal efficiency to a limited extent.
Two-stage air heating furnaces as shown in U.S. Pat. No. 2,738,785 issued Mar. 20, 1956 are known but have not become commercially successful due to apparent lack of improvement of efficiency, particularly in the second stage.
Domestic-type furnaces must be adapted to meet several stringent requirements. For one, they must meet the approval standards such as CGA standards for forced-air furnaces. As well, new furnace models must be capable of being produced economically and to incorporate design features and materials of construction which are familiar to the trade for ease of production and/or maintenance.
It is accordingly an object of the present invention to provide a furnace adapted for use as a domestic furnace which has a significantly higher steady state and seasonal efficiency than conventional furnaces either operating alone or in conjunction with heat-saving attachments.
The improved furnace systems in accordance with the present invention are capable of attaining significantly higher fuel savings, compared to conventional furnaces with or without fuel saving devices, without sacrificing safety of these furnace systems.
As has been indicated, conventional gas-fired furnaces have an overall cyclic efficiency in the order of about 50 to 65%. In accordance with the furnace systems in the present invention, this efficiency can be appreciably increased so that, on a seasonal basis, the efficiency rating is in the order of 90% or better.